Transmitter for telephony



Jan. 2, 1923. LMLLQZQL H. J. ROUND.

TRANSMITTER FOR TELEPHONY.

FILED MAR-31, 1920.

Fatentecl Jan; 2, H233, I

- entree iaerenr cornice...

.HENRY JUSEPH ROUND, 0F LONDQN, ENGLAND, AQQTGNOE TO THE ,RADKOCURJPURA-TTQZF Q15 AMERICA, @F NEW- YORK, N. 52.,

A CQEJPURATIQN @F DELAWARE.

TRANSMITTER FQR TELEPHONY.,

Application filed march 31, 1929. I Serial Katmai? To all whom it may(concern:

Be it known that T, HENRY. Josnrrr ROUND, a subject of the King of GreatBritain, residin at 9 Woodberry Crescent, Muswell Hill, ondon, England,have invented new and useful Improvements in Transmitters for Telephony,of which the following is a specification.

This invention relates tov improvements in telephone transmitters of thet pe employing thermionic generators, an its object is to provide anarrangement whereby the generation of the continuous waves upon whichthe sound vibrations are impressed is controlled b the voice.

lit is wel known that the necessity for starting these continuous waveswhen it is desired to speak and for stopping them when it is desired tolisten is an impediment to free conversation as some switching device isusually required. v

According to this invention, means are provided whereby the voice itselfcauses:

both direct and alternating current, to be fed to a thermionicgenerator, the direct current, starting with the voice and stopping withthe voice, causes continuous waves to be generated while the alternatingcurrent causes the amplitude of these waves to be varied.

Preferably there is connected to the generator a large condenserconnected through a rectifier .to a transformer in the microphonecircuit' so that any Vibrations of the current in this circuit give thecondenser a charge which leaks rapidly away when the vibrations cease.The microphone is also connected to the primary of another transformer,usually in series with the large condenser and with a smaller one whichforms part of the oscillatory circuit.

This invention is illustrated by the accompanying drawing which shows itas applied to wireless telephony, Fig. 1 being a diagrammaticillustration of circuit arondary of T2 to the anode of the generator Vconnected to an aerial A. Tt'will be seen that since there is no sourceof potential such as the usual battery in the anode filament circuit ofV there will be no generation of oscillations by V until speech iscommenced when direct current w1ll be fed to the anode filam nt circuitfrom the charge in condenser (1', due to the transformer T1 and therectifier lit. The valve will then generate continuous waves theamplitude of which will be varied according to the speech by thealmrnating currents fed to the valve by the transformer T2 and theenvelope of the oscillations will correspond to the alternating currentwave and the speech will be reproduced at the receiving end withoutdistortion.

If the windings of T1 and T2 are such that a fairly large part of theenergy goes to the production of the direct current and only a smallerpart to the production of the alternating current, a rapid rise ofdirect current potential is obtained on the condenser as soon as speechstarts.

In order, however, to prevent this potential from rising to more than adefinite value, a limiting device may be employed which by limiting thepotential on (1 speeds up the dying away when the speech stops, as shownin Figure 2, where'rectifier valve R1 and battery B1 represent thelimiting device. 1 I

Tn this arrangement also is shown the alternating 'current produced bythe voice as acting on the grid of the generating valve V and theresulting oscillations are then magnified by the Valve circuit V2,having a high voltage input source HT connected across the plate andfilament. 'The magnified oscillations are supplied by the valve V2 tothe antenna A. j

These two v -,diagrarns are shown merely as illustrations of theinvention which is not limited to these circuits in particular.

The continuous waves may be varied by the voice in any of the well knownmethods.

What I claim is r v 1. In a telephone transmitter, the combination of athermionic generator, a rectifier and means whereby the voice causesdirect current to be supplied to the generator fro the rectifier.

2. lina telephone transmitter, the combination of a thermionicgenerator, a rect1fier,

rectifier and a condenser, a three electrode",

valve comprising a plate, filament and grid,

said plate andfilament being connected to said condenser, means forcoupling said grid to the first mentioned circuit and an oscillationcircuit connected to the plate and filasaid plate and filament beingconnected tosaid condenser, means for coupling said gridto the firstmentioned circuit and an oscilla:

tion circuit connectedto the plate and fila-' ment, and means forcoupling the grid to the oscillation circuit. r v

18. In a telephone transmitter, the combi nation of a thermionicgenerator, a rectifier, a condenser cooperating With the generator,

and means whereby the voice causes current to be supplied to saidrectifier.

said condenser from 19. In. a telephone transmitter, the combi nation ofa thermionic generator, a rectifier, a condenser cooperating With thegenerator, means whereby the voice causes current to be supplied to'thecondenser from the rectifier, and means whereby the voice is caused tovary the high frequency current produced by the enerator.

nation of a microphone, a source of current, two transformers,arectifier, a condenser connected in series With the rectifier and na tlephone transmitter, the combir with the secondary'of onetransformer, adevice adapted to limit the potential on the condenser, and a thermionicgenerator comprising a filament, a grid and an anode, the anode beingconnected to one side of the condenser and the grid being connected tothe other side of the condenser through the secondary of the .secondtransformer.

In testimony that l[ claim the foregoing as my invention l have signedmy name this 23rd day of February 1920.'

v HENRY JUSEPH retire;

